Mr. Alexander has been coming to this corner of London's Hyde Park every Sunday for the past year. A video producer on weekdays and a "revealer of truths" weekends, he wants to alert people to the fact that "the world is ending as we speak."

He adds: "You can see it in the freak weather incidents, the wars in the Middle East, the credit crunch.... And all of this is being orchestrated."

By whom?

"By them." He nods in toward central London.

Anyone overhearing might half-expect to turn and see "Matrix"-style men in black and shades ready to haul him away in a van with no-number plates. But there is only a smattering of tourists and Londoners, umbrellas at the ready, listening to speeches on everything from Greek democracy to fast food to Armageddon.

The clouds spit down some drizzle, and Alexander observes seriously that even though the US government experiments with weather control "I don't think they'd deploy it just to keep me from speaking."

He ascends his stepladder, and starts speaking. Before long, 20 people have gathered, some listen intently, others heckle wildly.

• • •

Since it was set up in 1872, Speakers' Corner in Hyde Park has been one of the world's best-known forums for public debate – and public displays of intellectual eccentricity.

It's big day is Sunday,and the likes of Karl Marx, Vladimir Lenin, and George Orwell have come to listen. Intended as a space for free and open discussion, anyone can turn up and speak on any topic – so long as they don't swear excessively or incite hatred or violence. Police officers stroll through the corner every hour or so, to keep an eye – and an ear – on proceedings.

Now, a new charity – the Speakers' Corner Trust, whose founding patron is Vaclav Havel, the playwright and human rights activist who was the first president of the post-Communist Czech Republic – wants to breathe life back into civil society in Britain by setting up many more corner-style spaces where citizens can engage in face-to-face debate.

"Our aim is to get people exchanging ideas," says Peter Bradley, codirector of the trust.

"Rights are like muscles," he says. "If you don't exercise them, they become weak and flabby. And British people are not exercising their right to free speech. It's the mark of democracy to have active debate – and we want to encourage people to discuss the big issues with each other."

The trust tested a new Speakers' Corner in Nottingham, England, earlier this year. Mr. Bradley says it generated "excellent debate about politics, climate change, family life." A space is being paved and landscaped for a permanent Speakers' Corner in Nottingham's historic Market Square. It's set to open for the business of loud and rowdy debate in the autumn.

The founding of the original Speakers' Corner in Hyde Park is intimately bound with the birth of free speech and democracy in Britain. In 1866, the Reform League – which campaigned for the right of all men to vote, rather than just the posh and privileged – organized a public meeting in Hyde Park. Thousands turned up, broke through a 1,700-man police blockade, and took over the north-east corner of the park where they held impassioned discussions. This led to deliberation in Parliament about the right to free speech in Hyde Park – and in 1872, the Royal Parks and Gardens Regulation Act was passed, giving over that park corner to public speaking.

But in recent years, Speakers' Corner has been more zany than serious. Tourists turn up to gawk in wide-eyed amusement at a lineup of eccentric speakers. Can the corner really be a model for re-energizing "active debate" about "big issues?"

• • •

The drizzle has eased. Kirkley Greenwell, a young Christian woman from Baltimore, Md., who lives in London, is debating with an Islamic speaker who is perched on a wooden crate. He's arguing that the gnostic gospels should be included in the Christian canon; she argues articulately against it. "They say that women must become men to enter the Kingdom of God – and that's nonsense!" she says with righteous fury. The speaker seems lost for words.

"I like coming to Speakers' Corner," Ms. Greenwell says. "I wouldn't say it is enlightening, but it is certainly stimulating. I've heard debates on Africa, junk food, the monarchy, socialism, everything. And usually I get involved."

Isaac Berling, a college student on holiday from Minnesota, is less impressed: "It's more preachy than I thought it would be. The speakers are holding forth, but the audience is holding back. Except for that drunk guy." He points to a man hysterically heckling an unfortunate speaker.

Others, unlike Mr. Berling, are enjoying themselves. There's a debate about whether Hillary Clinton is ruining the Democrats' chances of presidential victory by staying in the primary campaign for so long. "We could do with public debate like this in Washington," says an American visitor in the audience.

• • •

"My view is that Speakers' Corner has been hijacked by eccentrics," says Dan Travis, founder of the Brighton Salon in Brighton, a bohemian enclave on the south coast of England with a large gay and lesbian community.

Mr. Travis, a sports educator by profession, set up the salon there last year to address people's "frustration with the smallness of public discussion today." He wanted a space where people could "debate the bigger issues of our time." It is modeled, he says, on the discussion salons that sprung up in Europe at the end of the 18th century and hosted "the great thinkers of the time: Diderot, Rousseau, Voltaire." Travis believes that Speakers' Corner is too much of a "free-for-all."

He wants more structure: "People need time to consider the issues before entering a debate. Having a speaker deliver a talk and then take questions and points from the floor, where most of the audience members will have done some related reading beforehand ... [that] allows for a detailed examination of an issue."

Yet Peter Bradley insists that the new corners will indeed be different from Hyde Park. "The original corner is our inspiration, but it's not our model," he says. "That corner is a destination – people, especially tourists, travel there especially to witness something out of the ordinary. It is away from the hustle and bustle of everyday London, and it has become a kind of show.

"In contrast, the new corners, like the one in Nottingham, will be in the heart of city centers. So they will attract people going about their daily business. You can go there during your lunch break, or on your way to work; they will be part of our daily lives."

Mr. Bradley says the original Speakers' Corner still shows the value of "face-to-face debate."

"And in our era of 'virtual debate' – in online forums where many remain anonymous and sometimes become trite and offensive – that is worth celebrating. In face-to-face engagement, you have to account for your views; it can be a humanizing, civilizing, educating experience."

• • •

The grey clouds have parted; the sun is peaking through. One of the most popular speakers of the day – a large, loud man wearing a hat with two red horns sticking out of it – won't give his name, "because I come here to say what I think, not for glory."

What's his take on creating more Corners?

"You know, Speakers' Corner is like a therapeutic institution," he says. "People come here to get validation for their views, or to let off steam. It isn't always pretty, but so what? If it helps people, that's cool."